This prospective animal study is designed to examine the feasibility of utilizing hydroxyapatite to augment the posterior portion of the upper jaw (maxilla). The need for this capability was presented at the National Institute of Health Consensus Conference at which time it was established at 18% of the Americans, 55 - 64 years old, are edentulous in the posterior portion of their maxilla. The inadequate bone volume in the posterior portion of the edentulous maxilla has previously been addressed by utilizing iliac bone grafts or bone grafts from other sites with the concomitant donor site morbidity and quantitative limitations being accepted as necessary to meet the patients maxillary reconstructive needs. The availability of porous hydroxyapatite (PHA) presents an alternate to autogenous bone grafts, which may meet the needs of posterior maxillary edentulism without autogenous bone graft cost or morbidity. This study will determine the percentage of bone ingrowth into porous hydroxyapatite when it is used to augment the antral floor. Additionally, this study will determine if there is a significant difference in the percentage of bone ingrowth into two different types of porous hydroxyapatite. These objectives will be met by utilizing adult goats who will undergo posterior maxillary edentulation and three months of healing prior to a sinus lift procedure being performed. The sinus lift procedure consists of the development of a mucoperosteal flap to expose the lateral antral wall which is then displaced medially into the sinus, permitting sinus floor augmentation with PHA. This study will then assess the bone ingrowth into the PHA at 4, 8, and 12 month intervals. The quantification will be computer based histometry utilizing back scatter images from a scanning electron microscope which will result in trimodal (soft tissue-bone-hydroxyapatite) density histograms.